Samsung — Pre-book offer item not delivered

I have pre-booked a Samsung Galaxy tab s8+ tablet on 25th Feb 2022. As the pre-booking offer I was supposed to get a Keyboard book cover along with the tablet. However when I have received the product, there was no keyboard cover included.
Amazon is denying that there was no such offer and not ready to help.
In the Amazon India website, Samsung answered multiple times that the keyboard cover will be included.
Also in Samsung website there was a document stating that the keyboard cover can be redeemed from samsung shop app later. I have followed the steps, but it is showing I am not eligible for it.
In this situation noone is helping.
Seems that I have made a mistake by keeping trust on brand Samsung.